Processor Thermal Solution Design Application Note Publ
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AMD-K6
Processor
Thermal Solution Design
Application Note
Publication 21085 Rev: Issue Date: February 1999 Amendment/0
contents this document provided connection with Advanced Micro Devices, Inc. ("AMD") products. makes representations warranties with respect accuracy completeness contents this publication reserves right make changes specifications product descriptions time without notice. license, whether express, implied, arising estoppel otherwise, intellectual property rights granted this publication. Except forth AMD's Standard Terms Conditions Sale, assumes liability whatsoever, disclaims express implied warranty, relating products including, limited implied warranty merchantability, fitness particular purpose, infringement intellectual property right. AMD's products designed, intended, authorized warranted components systems intended surgical implant into body, other applications intended support sustain life, other application which failure AMD's product could create situation where personal injury, death, severe property environmental damage occur. reserves right discontinue make changes products time without notice. 1999 Advanced Micro Devices, Inc. rights reserved.
Trademarks AMD, logo, combinations thereof trademarks, AMD-K6 registered trademark Advanced Micro Devices, Inc. Other product names used this publication identification purposes only trademarks their respective companies.
21085I/0-February 1999
AMD-K6® Processor Thermal Solution Design
Contents
Revision History Introduction System Conditions Thermal Solutions Heatsink Heat Dissipation Path Interface Materials. Layout Airflow Considerations
Voltage Regulator Heatsink Airflow Management System Design Airflow Management Form Factor Additional Fans. Thermal Evaluation Measuring Case Temperature Thermal Power Utility Recommended Thermal Solutions AMD-K6® Processor Family Additional Information.
Contents
AMD-K6® Processor Thermal Solution Design
21085I/0-February 1999
Contents
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AMD-K6® Processor Thermal Solution Design
List Figures
Figure Passive Heatsink Thermal Model Figure Processor Heat Dissipation Path Figure CPGA Package Thermal Resistance Model. Figure Voltage Regulator Placement Figure Airflow Heatsink with Figure Airflow Path Dual-Fan System Figure Airflow Path Form-Factor System Figure Standard Mid-Tower Case Figure Measuring Case Temperature.
List Tables
Table Table AMD-K6 Processor Family TCASE Specifications Summary Chassis Configurations
List Figures Tables
AMD-K6® Processor Thermal Solution Design
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List Figures Tables
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AMD-K6® Processor Thermal Solution Design
Revision History
Date March 1998 March 1998 March 1998 March 1998 1998 1998 1998 1998 1998 1998 1998 1998 Description Improved detail Figure "Passive Heatsink Thermal Model," page Figure "Voltage Regulator Placement," page Added system design considerations fansink implementations. "Heatsink Fan" page Combined recommended fansink solutions into table. Table "AMD-K6® Processor Model Fansink Recommendations." Added fansink manufacturers models Table "Manufacturer Contact List." Revised "Recommended Fansinks AMD-K6® Processor Model AMD-K6®-2 Processor Model include AMD-K6-2 processor Model information. Revised Table "AMD-K6® Processor Model Fansink Recommendations" Table "Manufacturer Contact List." Added Table "Additional AMD-K6® Processor Models AMD-K6®-2 Processor Model Fansink Recommendations." Removed package thermal specifications tables. thermal specifications, added reference applicable AMD-K6 AMD-K6-2 Processor Data Sheets. Revised Table "AMD-K6® Processor Model Fansink Recommendations" Table "Manufacturer Contact List." Added recommended AMD-K6-2 processor thermal solutions Table "Additional AMD-K6® Processor Model AMD-K6®-2 Processor Model Fansink Recommendations." Revised Figure "Measuring Case Temperature," page Combined paragraphs "Recommended Fansinks AMD-K6® Processor Model "Recommended Fansinks AMD-K6® Processor Model AMD-K6®-2 Processor Model into paragraph. Replaced Recommended Fansinks (Tables Manufacturer Contact List (Table with reference Recommended Thermal Solution section website. Added references AMD-K6-III processor, where applicable. Added Table "AMD-K6® Processor Family TCASE Specifications." Revised "Thermal Power Utility" page reflect latest recommended utility.
1998 1999 1999 1999
Revision History
AMD-K6® Processor Thermal Solution Design
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Revision History
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AMD-K6® Processor Thermal Solution Design
Application Note
AMD-K6
Processor Thermal Solution Design
Unless otherwise noted, information this application note pertains processors AMD-K6® family, which includes AMD-K6 processor (Models AMD-K6-2 processor (Model AMD-K6-III processor (Model
Introduction
operating specification AMD-K6 processor family calls case temperature (TCASE) range TCASE Max. important maintain case temperature specification exceeded, result functional failures, damage device, reduction long term reliability. Table page lists TCASE specifications desktop AMD-K6 processor family. Table
AMD-K6® AMD-K6-2 AMD-K6-III
Note:
AMD-K6® Processor Family TCASE Specifications
Minimum Maximum 70°C 60°C, 65°C, 70°C 65°C Note
Processor Family
Refer AMD-K6®-2 Processor Data Sheet, order# 21850 operating specifications they apply each AMD-K6-2 offering.
Introduction
AMD-K6® Processor Thermal Solution Design
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effective thermal management system best maintain case temperature within specification. addition thermal characteristics power dissipation processor, temperature processor case dependent internal ambient temperature velocity. internal ambient temperature affected several variables electronic components, peripherals, thermal characteristics chassis, external ambient temperature. Thermal management consists heatsinks, thermal interface materials, heatsink clips, fans, chassis ventilation, component placement. This application note intended guide system designer through process developing effective thermal solution AMD-K6 processor. information about thermal specifications following AMD-K6 processors:
AMD-K6 processor Model (0.35-µm process technology) AMD-K6 processor Model (0.25-µm process technology), refer AMD-K6® Processor Data Sheet, order# 20695. AMD-K6-2 processor Model (0.25-µm process technology), refer AMD-K6®-2 Processor Data Sheet, order# 21850. AMD-K6-III processor Model (0.25-µm process technology), refer AMD-K6®-III Processor Data Sheet, order# 21918.
System Conditions
environmental specifications most systems guarantee chassis/system boxes result internal 10°C increase temperature over external ambient temperature. general, this means thermal solution should designed allow internal ambient (TA) 45°C.
Introduction
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AMD-K6® Processor Thermal Solution Design
Thermal Solutions
Heatsink
Figure page shows thermal model processor with passive thermal solution. thermal resistance heatsink determined heat dissipation surface area, material shape heatsink, airflow volume through heatsink. general, larger surface area lower thermal resistance. Heatsink designs fins increase amount dissipating surface area contact with ambient air. larger surface area usually results lower thermal resistance. Some designs implement cross-cutting along fins allow omnidirectional airflow through heatsink. required thermal resistance heatsink calculated using following example:
65°C 45°C PMAX 29.5W
Then: 20°C 0.678°C 29.5W Where:
Processor case temperature Ambient temperature
PMAX Maximum power consumption Case-to-ambient thermal resistance
Using interface material with thermal resistance approximately 0.20 (i.e. thermal grease), required thermal resistance heatsink (SA) calculated follows:
0.678 0.20 0.478 °C/W
Where:
Case-to-ambient thermal resistance Interface material thermal resistance Sink-to-ambient thermal resistance
Thermal Solutions
AMD-K6® Processor Thermal Solution Design
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Ambient
Temperature Delta (Case-to-Ambient) Thermal Resistance (°C/W)
Sink Case
Figure Passive Heatsink Thermal Model
Heat Dissipation Path
Figure illustrates heat dissipation path processor. lower thermal resistance between processor junction case, most heat generated processor transferred from surface case. small amount heat transferred from bottom side processor safely ignored high thermal resistance (the processor socket blocks convection).
Ambient Temperature
Thin Case Temperature
Figure Processor Heat Dissipation Path Figure page illustrates overall thermal resistance model socketed AMD-K6 processor with heatsink ached. herma resistance primary heat dissipation path much lower than secondary heat dissipation path. Therefore, most heat transferred from side processor. Figure represents thermal resistance from case ambient. includes thermal resistance thermal interface material heatsink, which must considered when designing thermal solution AMD-K6 processor. Thermal Solutions
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AMD-K6® Processor Thermal Solution Design
Thin Ceramic substrate Heat Sink Clip Print-Circuit Board
Heat Sink Thermal Interface Material Socket
Primary Heat Dissipation Path
Radiation Convection
Ambient
External Resistance
Heat Sink Thermal Interface Material Thin Grease Silicon
Case Temperature
Chip Junction
Junction Temperature
Underfill
Package
Bumps Ceramic Substrate Package Pins Print-Circuit Board Socket
External Resistance
Radiation Convection
Secondary Heat Dissipation Path
Figure CPGA Package Thermal Resistance Model
Interface Materials
interface material used between heatsink processor important. purpose this material fill microscopic gaps ensure thermally efficient path established heat flow from package into heatsink. There several different types thermally conductive interface material today. most common grease, wax, thermal pads/tapes, epoxy. While interfaces (pads tapes) often easiest use, they have poorest thermal resistance. They recommended because small pockets trapped during installation. paste interfaces (grease, gel, wax, epoxy) have lower thermal resistances allow bubbles migrate interface material. Although epoxy, when handled correctly, provide reasonable thermal interface, reliable mechanical attachment. Caution should also taken with pre-applied waxes, because pockets poor thermal conductor) Thermal Solutions
AMD-K6® Processor Thermal Solution Design
21085I/0-February 1999
trap eath heats embly. recommends grease gels thermal interfaces. These materials able maintain lowest thermal resistance more consistently. general, these materials achieve thermal resistance 0.15 0.3°C/W. application interface material, addition material type, also important. purpose simply fill microscopic gaps ensure thermally efficient path heat transfer. Only thin layer interface material desired between heatsink processor. Excessive amounts interface material will restrict flow heat heatsink thereby make thermal solution less effective. light weight most heatsinks, mechanical clips recommended method attachment. addition providing stability, clips provide approximately 10-15 pounds downward pressure heatsink minimize thermal resistance thermal interface material.
Layout Airflow Considerations
Voltage Regulator
Voltage regulators, typically power transistors, used provide core voltages processor. most designs, separate heatsinks also required dissipate heat from power transistors. processor heatsink fins should aligned parallel chassis airflow voltage regulators shown Figure page With this alignment, heat generated voltage regulators minimal effect processor.
Layout Airflow Considerations
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AMD-K6® Processor Thermal Solution Design
Voltage Regulator (VCC Core)
Heatsink Fins Aligned With Airflow
Airflow
Voltage Regulator (VCC I/O)
Figure Voltage Regulator Placement
Heatsink
heatsink combination, fansink, deliver even better thermal performance than heatsink alone. More importantly, airflow requirements system design critical with fansink. pulls from above fan, through heatsink, heatsink sides. When using fansink solution, best location voltage regulators side processor, path exiting fansink (See Figure page Such location guarantees that heatsinks both processor regulator receive adequate airflow. Fansinks more effective when following design techniques employed:
avoid impeding airflow within chassis fansink, route ribbon cables between system motherboard chassis drive bays. provide sufficient volume fansink, maintain inch clearance above fansink.
Layout Airflow Considerations
AMD-K6® Processor Thermal Solution Design
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Airflow
Ideal areas voltage regulator
Figure Airflow Heatsink with
Airflow Management System Design
Complete airflow management system important. addition speed volume air, path also important. Figure shows airflow dual-fan system. front pulls cool into system through intake slots chassis. power supply acts exhaust forces chassis. thermal performance heatsink maximized located shaded area with fins oriented parallel airflow path.
Main Board
Vents Front
Drive Bays
Figure Airflow Path Dual-Fan System Layout Airflow Considerations
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AMD-K6® Processor Thermal Solution Design
Airflow Management Form Factor
Figure shows airflow management system using form-factor. orientation power supply motherboard modified platform design. power supply generates airflow through chassis across processor. processor located near power supply where receive maximum airflow without auxiliary fan. This arrangement significantly improves airflow across processor with minimum installation cost.
Main Board
Vents
Drive
Bays
Figure Airflow Path Form-Factor System
Additional Fans
Additional fans enhance effectiveness airflow within chassis. Table page summarizes effect different numbers configurations fans chassis. purpose fans improve circulation within chassis. fans used this experiment were chosen existing mountings chassis. front 80-mm 35-CFM rear 60-mm 25-CFM fan. goal better circulation reduce ambient temperature inside chassis.
Layout Airflow Considerations
AMD-K6® Processor Thermal Solution Design
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given chassis, different combinations fans were tested. tests were performed oven with constant temperature 35°C, internal ambient temperature thermocouple located inches from processor shown Figure page control case with added fans chassis resulted internal ambient 48.2°C. best improvement ambient temperature observed with configuration single added chassis intake rear wall system chassis. This placement resulted decrease ambient temperature from 48.2°C 43.6°C. Table complete summary chassis combinations. Also, note that best case temperature (TCASE) processor obtained approximately 44.4°C. shown test, lowest ambient temperature always indicator lowest CASE Ambient temperature very dependent airflow path measured. only completely verify thermal solution measure TCASE. Table Summary Chassis Configurations
Test 68.8°C 48.2°C Test Intake 69°C 48.7°C Test Exhaust Intake 64.1°C 44.4°C Test Intake 65.9°C 43.6°C
Thermal Test Condition Rear Wall System Front Wall System Processor, TCASE Internal Ambient Temperature
Layout Airflow Considerations
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AMD-K6® Processor Thermal Solution Design
Rear Power Supply
Front
Drive Bays
AMD-K6® Processor Regulator Heatsink
Inside Ambient Thermocouple
Intake Vent
Figure Standard Mid-Tower Case
Thermal Evaluation
Measuring Case Temperature
processor case temperature measured ensure that specification. This temperature should measured center package where most heat dissipated. Figure page shows correct location measuring case temperature. heatsink installed while measuring, thermocouple must installed into heatsink small hole drilled through heatsink base (for example, 1/16 inch). thermocouple then attached base heatsink small hole filled using thermal epoxy, allowing thermocouple touch processor case. Thermal Evaluation
AMD-K6® Processor Thermal Solution Design
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Thermally Conductive Epoxy
Thermocouple
Figure Measuring Case Temperature
Thermal Power Utility
software utility been developed assist testing thermal solutions. This utility executes tight loop instructions whose addressing data have been defined AMD-K6 processor state that dissipates maximum thermal power. This utility used determine given thermal solution sufficient maintain specified TCASE limit. this utility, execute program, Maxpwr99.exe follows: (Note: execute utility window with memory manager loaded.)
c:\>Maxpwr99.exe
program executes infinite loop until exited. While executing, processor's case temperature measured. addition, actual power dissipation should determined measuring voltage current supplied processor. Note: daughter card allow processor current measured series with Ohmmeter. Take measurements close processor (use short lead wires). processor power less than maximum thermal power specification, linear estimate must used determine thermal solution maintains case temperature below specified limit.
Thermal Evaluation
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AMD-K6® Processor Thermal Solution Design
Maxpwr99.exe utility available under nondisclosure information.
Recommended Thermal Solutions AMD-K6® Processor Family
continually works with heatsink manufacturers identify thermal solutions AMD-K6 processor family. list solutions that maintain case temperature AMD-K6 processor below specified maximum temperature available Recommended Thermal Solutions section website, www.amd.com. Most solutions listed available as-is ordered combination from manufacturer. These solutions available heatsink combination. Other solutions require specific fan, mounted heatsink, capable sufficient flow (for example, 233-MHz AMD-K6 processor). such cases, heatsink ordered separately from each manufacturer.
Additional Information
more information about following AMD-K6 processors:
AMD-K6 processor Models AMD-K6® Processor Data Sheet, order# 20695 contact your local sales representative. AMD-K6-2 processor Model AMD-K6®-2 Processor Data Sheet, order# 21850 contact your local sales representative. AMD-K6-III processor Model AMD-K6®-III Processor Data Sheet, order# 21918 contact your local sales representative.
Additional Information
AMD-K6® Processor Thermal Solution Design
21085I/0-February 1999
Additional Information
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